Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #41552

Re: CSV, lists, and functions

Show all headers | View raw

On 03/19/2013 06:59 PM, C.T. wrote:
> Hello,
>
> Currently doing a project for class an I'm stuck. I have a csv file that I'm suppose to extract some information from. I've created a function that ignores the first six lines of the csv file and creates a list of values in a particular column. Here is the code:
>
>
> def get_values(file, index):
>
>      '''(file object, int) -> list
>      Return a list of states and corresponding values at a prticular index in file.'''
>
>      values_list = []
>      file.readlines(900)#skipping first 6 lines of file
>      for line in file:
>          line_list = line.split(',')
>          values_list.append(line_list[index])
>
>      return values_list
>
>
>
> #Prompt for file and prompt again if file is not found
> while True:
>      try:
>          file_name = input('Enter in file name: ')
>          input_file = open( file_name, 'r')
>          break
>
>      except IOError:
>           print('File not found.')
>
> heart_list = get_values(input_file, 1)
> motor_list = get_values(input_file, 4)
>
> I can see a list of values for heart_list, but when I print the motor_list I get back an empty list. I think its because I'm not closing the file before calling the function again, but I don't want to prompt for the same file over and over again because I need to pull at least 10 columns from this csv files and turn them into lists. Any help is appreciated.
>

f.seek(0)

will reposition the file to the beginning.

But you should switch to using the csv module.  And unless you have data 
that consists of millions of lines, you should just read the whole thing 
in once, and then extract the various columns by simple list 
manipulations and/or comprehensions.


-- 
DaveA

Back to comp.lang.python | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

CSV, lists, and functions "C.T." <swilks06@gmail.com> - 2013-03-19 15:59 -0700
  Re: CSV, lists, and functions Roy Smith <roy@panix.com> - 2013-03-19 19:19 -0400
  Re: CSV, lists, and functions Dave Angel <davea@davea.name> - 2013-03-19 21:29 -0400
    Re: CSV, lists, and functions Roy Smith <roy@panix.com> - 2013-03-19 21:37 -0400
      Re: CSV, lists, and functions rusi <rustompmody@gmail.com> - 2013-03-20 01:11 -0700

csiph-web